Detection rules › Splunk

Suspicious Parent Process for lsass.exe or services.exe (Windows Event Log)

Group by
_time, host
Source
github.com/anvilogic-forge/armory

This use case detects when either the Windows local security authority subsystem (lsass.exe) or service control manager (services.exe) are executed as a child from an unexpected parent process. This can indicate process injection/hollowing, masquerading, or other suspicious activity. The expected parent process for these services is wininit.exe.

MITRE ATT&CK coverage

References

Telemetry coverage

Rule body

id: '16171.24332'
title: Suspicious Parent Process for lsass.exe or services.exe
description: This use case detects when either the Windows local security authority
  subsystem (lsass.exe) or service control manager (services.exe) are executed as
  a child from an unexpected parent process. This can indicate process injection/hollowing,
  masquerading, or other suspicious activity. The expected parent process for these
  services is wininit.exe.
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
  "<EventID>4688<" OR Type=Process) ("lsass.exe" OR "services.exe") | regex process_path="(?i)\x5csystem32\x5c(lsass|services)\.exe"|
  regex parent_process_name!="(?i)wininit\.exe"| where isnotnull(parent_process_name)
  and not match(parent_process_name, "^-$") | table _time, host, user process, process_*,
  parent_process_name, parent_process_* | bin span=1s | stats values(*) as * by _time,
  host '
techniques:
- defense-evasion:masquerading:masquerade task or service
- defense-evasion:process injection
technique_id:
- T1036.004
- T1055
data_category:
- Windows event logs
references:
- https://andreafortuna.org/2017/06/15/standard-windows-processes-a-brief-reference/

Stages and Predicates

Stage 1: search

`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) ("lsass.exe" OR "services.exe")

Stage 2: regex

| regex process_path="(?i)\x5csystem32\x5c(lsass|services)\.exe"

Stage 3: regex

| regex parent_process_name!="(?i)wininit\.exe"

Stage 4: where

| where isnotnull(parent_process_name) and not match(parent_process_name, "^-$")

Stage 5: table

| table _time, host, user process, process_*, parent_process_name, parent_process_*

Stage 6: bucket

| bin span=1s

Stage 7: stats

| stats values(*) as * by _time, host

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
parent_process_nameregex_match"(?i)wininit.exe"excludes:parent_process_name
parent_process_nameregex_match"^-$"excludes:parent_process_name

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
EventCodeeq
  • 4688 corpus 317 (splunk 283, kusto 33, elastic 1)
field:"EventID" kind:eq value:"4688"
parent_process_nameis_not_null
  • (no value, null check)
field:"parent_process_name" kind:is_not_null
process_pathregex_match
  • "(?i)\x5csystem32\x5c(lsass|services).exe" corpus 2 (splunk 2)
field:"process_name" kind:regex_match

Search terms

These SPL tokens match against raw event text.

StageTerm
1"<EventID>4688<"
1"lsass.exe"
1"services.exe"